/*
 * Copyright 2011-2012 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.sabayframework.mem.impl.disk;

import java.io.IOException;

/**
 * A transactional storage for arbitrary data records.
 * */
public interface DiskStorage {
	/**
	 * Read data from given address. 
	 * This method will return record committed by the latest transaction.
	 * @return byte array with data. Returns byte array with zero length if address 
	 * was not used before.
	 * */
	byte[] read(long address) throws IOException;
	/**
	 * Returns true if the file contains non zero-length data in given address.
	 * */
	boolean contains(long address) throws IOException;
	
	boolean isOpen() throws IOException;
	
	/**
	 * Optimize storage usage. 
	 * */
	void compact() throws IOException;
	
	void close() throws IOException;
	
	void delete() throws IOException;
	
	long getNumberOfRecords() throws IOException;
	
	long getFreeSpace() throws IOException;
	
	long getUsedSpace() throws IOException;
	
	DiskTransaction beginTransaction() throws IOException;
}
